Transition metal complexes containing substituted imidazole carbene as ligands and their application in oleds

ABSTRACT

Compounds having a metal M complexed to a ligand L containing a substituted imidazole carbene group, which is represented Formula (I), below: 
     
       
         
         
             
             
         
       
     
     wherein ring B is a 5-member aromatic heterocyclic ring containing at least one heteroatom selected from the group consisting of N, O, and S; wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclic ring; wherein R A  represents mono, di, tri, tetra substitutions or no substitution; wherein R 1  represents mono, di, or tri substitution or no substitution; wherein each R A , R 1  and R 2  is independently selected from various possible substituents; wherein Z 1  is nitrogen or carbon; and wherein the ligand is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate or hexadentate ligand. Devices, such as organic light emitting devices (OLEDs) that comprise such compounds are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/673,634, filed Jul. 19, 2012, the entire contents of which areincorporated herein by reference.

JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to organic light emitting devices (OLEDs).More specifically, the invention relates to phosphorescent lightemitting materials that may have improved operational lifetime.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

A new type of light emitting material is provided. This new class ofmaterial includes compounds having a metal M₁ complexed to a ligand L₃containing a substituted imidazole carbene group, which is representedFormula (I), below:

wherein ring B is a 5-member aromatic heterocyclic ring containing atleast one heteroatom selected from the group consisting of N, O, and S;wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclicring; wherein R_(A) represents mono, di, tri, tetra substitutions or nosubstitution; wherein R₁ represents mono, di, or tri substitution or nosubstitution; wherein each R_(A), R₁ and R₂ is independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein any twoadjacent substituents are optionally joined to form a ring, which can befurther substituted; wherein Z₁ is nitrogen or carbon; and wherein theligand L₃ is optionally linked with other ligands to comprise atridentate, tetradentate, pentadentate or hexadentate ligand.

Any suitable metal M₁ can be used in the above complexes. In someembodiments, the ligand L₃ is complexed to a metal selected from thegroup consisting of: Ir, Rh, Re, Ru, Os, Pt, Au, and Cu. In some furtherembodiments, the metal M₁ in the complex is Ir or Pt.

In some further embodiments, the complex comprises a ligand L₃ that isselected from the group consisting of:

wherein A₁, A₂, and A₃ are independently selected from the groupconsisting of carbon, nitrogen, oxygen, and sulfur, and at least one ofA₁, A₂, and A₃ is not carbon. Other variables have the definitionsprovided above.

In some further such embodiments, the complex comprises a ligand L₃ thatis selected from the group consisting of:

wherein A₁ and A₃ are independently selected from the group consistingof oxygen, nitrogen, and sulfur; wherein R₃ represents mono, di, tri, ortetra substitution, or no substitution; and wherein R₃ is independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein anytwo adjacent substituents are optionally joined to form into a ring,which can be further substituted. Other variables have the definitionsprovided above.

In some further such embodiments, the complex comprises a ligand L₃ thatis selected from the group consisting of:

Substituted imidazole carbene complexes of Formula (II) are alsoprovided:

wherein -L₁-L₂- is a bidentate ligand selected from the group consistingof:

wherein R_(a), R_(b), and R_(c) represent mono, di, tri or tetrasubstitutions; wherein R_(a), R_(b), and R_(c) are each independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein anytwo adjacent substituents of R_(a), R_(b), and R_(c) are optionallyjoined to form a ring, which can be further substituted; and wherein nis 1, 2 or 3. Other variables have the definitions provided above.

Substituted imidazole carbene complexes of Formula (III) are alsoprovided:

wherein -L₁-L₂- is a bidentate ligand; and wherein m is 1 or 2. Othervariables have the definitions provided above.

Substituted imidazole carbene complexes of Formula (IV) are alsoprovided:

wherein -L₁-L₂- is a bidentate ligand; and wherein X is selected from agroup consisting of O, S, NR, CR′R″, SiR′R″; wherein R, R′, and R″ areindependently selected from the group consisting of alkyl, aryl andheteroaryl, wherein R′ and R″ are optionally linked; and wherein any twoadjacent substituents are optionally joined to form into a ring, whichcan be further substituted. Other variables have the definitionsprovided above.

Substituted imidazole carbene complexes of Formula (V) are alsoprovided:

where the variables have the definitions provided above.

Substituted imidazole carbene complexes of Formula (VI) are alsoprovided:

wherein X and Y are independently selected from a group consisting of O,S, NR, CR′R″, and SiR′R″; and wherein R, R′, and R″ are independentlyselected from the group consisting of alkyl, aryl, and heteroaryl; andwherein any two adjacent substituents are optionally joined to form intoa ring, which can be further substituted. The other variables have thedefinitions provided above.

Substituted imidazole carbene complexes of Formula (VII) are alsoprovided:

where the variables have the definitions provided above.

Substituted imidazole carbene complexes are provided, where thecomplexes are selected from the group consisting of:

Substituted imidazole carbene complexes are provided, where thecomplexes are selected from the group consisting of:

A device is also provided. The device may include an anode, a cathode,and an organic layer disposed between the anode and the cathode, wherethe organic layer comprises a compound of any of the foregoingembodiments (e.g., a substituted imidazole carbene complex).

The invention is not limited to any particular type of device. In someembodiments, the device is a consumer product. In some embodiments, thedevice is an organic light emitting device (OLED). In other embodiments,the device comprises a lighting panel.

In some embodiments, the organic layer of the device is an emissivelayer. In some such embodiments, the substituted imidazole carbenecomplex is an emissive dopant. In some other embodiments, thesubstituted imidazole carbene complex is a non-emissive dopant.

In some embodiments, the organic layer of the device further comprises ahost.

In some such embodiments, the host comprises a triphenylene containingbenzo-fused thiophene or benzo-fused furan, wherein any substituent inthe host is an unfused substituent independently selected from the groupconsisting of C_(n)H_(2n+1), OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂,N(Ar₁)(Ar₂), CH═CH—C_(n)H_(2n+1), C≡C—C_(2n+1), Ar₁, Ar₁-Ar₂,C_(n)H_(2n)—Ar₁, or no substitution, wherein n is from 1 to 10, andwherein Ar₁ and Ar₂ are independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof. In some such embodiments, the host is acompound selected from the group consisting of:

and combinations thereof.

In some other embodiments, the host comprises a metal complex. In somefurther embodiments, the host comprises at least one of the chemicalgroups selected from the group consisting of carbazole, dibenzothiphene,dibenzofuran, dibenzoselenophene, azacarbazole, aza-dibenzothiophene,aza-dibenzofuran, and aza-dibenzoselenophene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows a chemical formula representing a substituted imidazolecarbene ligand as disclosed herein.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-1”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. patent application Ser. No. 10/233,470, which is incorporated byreference in its entirety. Other suitable deposition methods includespin coating and other solution based processes. Solution basedprocesses are preferably carried out in nitrogen or an inert atmosphere.For the other layers, preferred methods include thermal evaporation.Preferred patterning methods include deposition through a mask, coldwelding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819,which are incorporated by reference in their entireties, and patterningassociated with some of the deposition methods such as ink-jet and OVJD.Other methods may also be used. The materials to be deposited may bemodified to make them compatible with a particular deposition method.For example, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including flatpanel displays, computer monitors, medical monitors, televisions,billboards, lights for interior or exterior illumination and/orsignaling, heads up displays, fully transparent displays, flexibledisplays, laser printers, telephones, cell phones, personal digitalassistants (PDAs), laptop computers, digital cameras, camcorders,viewfinders, micro-displays, vehicles, a large area wall, theater orstadium screen, or a sign. Various control mechanisms may be used tocontrol devices fabricated in accordance with the present invention,including passive matrix and active matrix. Many of the devices areintended for use in a temperature range comfortable to humans, such as18 degrees C. to 30 degrees C., and more preferably at room temperature(20-25 degrees C.).

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl,heterocyclic group, aryl, aromatic group, and heteroaryl are known tothe art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32,which are incorporated herein by reference.

Metal carbene complexes have a wide triplet energy gap, which makes themsuitable as blue emitters in phosphorescent OLEDs. However, thesecomplexes can exhibit instability when employed in certain devices,thereby leading to reduced operation lifetime. Without being bound bytheory, it is believed that such instability may be attributable to avariety of factors, including, but not limited to, long excitation delaylifetime, a mismatch of energy levels, and unbalanced electron/holefluexes. Substitution on the imidazole-carbene moiety can affect thecomplex's HOMO/LUMO energy levels, its emission spectrum, and itsemission quantum yield, thereby allowing one to fine-tune energy levels,emission spectra, and charge transport properties.

New metal complexes are provided, where the metal is complexed to atleast one ligand that contains a substituted imidazole carbene moiety.Such complexes may be advantageously used in OLEDs. Particularsubstituted imidazole carbene complexes are compounds comprising a metalM₁ complexed to a ligand L₃ of Formula (I):

wherein ring B is a 5-member aromatic heterocyclic ring containing atleast one heteroatom selected from the group consisting of N, O, and 5;wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclicring; wherein R_(A) represents mono, di, tri, tetra substitutions or nosubstitution; wherein R₁ represents mono, di, or tri substitution or nosubstitution; wherein each R_(A), R₁ and R₂ is independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein any twoadjacent substituents are optionally joined to form a ring, which can befurther substituted; wherein Z₁ is nitrogen or carbon; and wherein theligand L₃ is optionally linked with other ligands to comprise atridentate, tetradentate, pentadentate or hexadentate ligand.

Any suitable metal M₁ can be used in the above complexes. In someembodiments, the ligand L₃ is complexed to a metal M selected from thegroup consisting of: Ir, Rh, Re, Ru, Os, Pt, Au, and Cu. In some furtherembodiments, the metal M₁ in the complex is Ir or Pt.

In some further embodiments, the complex comprises a ligand L₃ that isselected from the group consisting of:

wherein A₁, A₂, and A₃ are independently selected from the groupconsisting of carbon, nitrogen, oxygen, and sulfur, and at least one ofA₁, A₂, and A₃ is not carbon. Other variables have the definitionsprovided above.

In some further such embodiments, the complex comprises a ligand L₃ thatis selected from the group consisting of:

wherein A₁ and A₃ are independently selected from the group consistingof oxygen, nitrogen, and sulfur; wherein R₃ represents mono, di, tri, ortetra substitution, or no substitution; and wherein R₃ is independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein anytwo adjacent substituents are optionally joined to form into a ring,which can be further substituted. Other variables have the definitionsprovided above.

In some further such embodiments, the complex comprises a ligand L₃ thatis selected from the group consisting of:

Substituted imidazole carbene complexes of Formula (II) are alsoprovided.

wherein -L₁-L₂- is a bidentate ligand selected from the group consistingof:

wherein R_(a), R_(b), and R_(c) represent mono, di, tri or tetrasubstitutions; wherein R_(a), R_(b), and R_(c) are each independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein anytwo adjacent substituents of R_(a), R_(b), and R_(c) are optionallyjoined to form a ring, which can be further substituted; and wherein nis 1, 2 or 3. Other variables have the definitions provided above.

Substituted imidazole carbene complexes of Formula (III) are alsoprovided:

wherein -L₁-L₂- is a bidentate ligand; and wherein m is 1 or 2. Othervariables have the definitions provided above.

Substituted imidazole carbene complexes of Formula (IV) are alsoprovided:

wherein -L₁-L₂- is a bidentate ligand; and wherein X is selected from agroup consisting of O, S, NR, CR′R″, SiR′R″; wherein R, R′, and R″ areindependently selected from the group consisting of alkyl, aryl andheteroaryl, wherein R′ and R″ are optionally linked; and wherein any twoadjacent substituents are optionally joined to form into a ring, whichcan be further substituted. Other variables have the definitionsprovided above.

Substituted imidazole carbene complexes of Formula (V) are alsoprovided:

where the variables have the definitions provided above.

Substituted imidazole carbene complexes of Formula (VI) are alsoprovided:

wherein X and Y are independently selected from a group consisting of O,S, NR, CR′R″, and SiR′R″; and wherein R, R′, and R″ are independentlyselected from the group consisting of alkyl, aryl, and heteroaryl; andwherein any two adjacent substituents are optionally joined to form intoa ring, which can be further substituted. The other variables have thedefinitions provided above.

Substituted imidazole carbene complexes of Formula (VII) are alsoprovided:

where the variables have the definitions provided above.

Substituted imidazole carbene complexes are provided, where thecomplexes are selected from the group consisting of:

Substituted imidazole carbene complexes are provided, where thecomplexes are selected from the group consisting of:

A device is also provided. The device may include an anode, a cathode,and an organic layer disposed between the anode and the cathode, wherethe organic layer comprises a compound of any of the foregoingembodiments (e.g., a substituted imidazole carbene complex).

The invention is not limited to any particular type of device. In someembodiments, the device is a consumer product. In some embodiments, thedevice is an organic light emitting device (OLED). In other embodiments,the device comprises a lighting panel.

In some embodiments, the organic layer of the device is an emissivelayer. In some such embodiments, the substituted imidazole carbenecomplex is an emissive dopant. In some other embodiments, thesubstituted imidazole carbene complex is a non-emissive dopant.

In some embodiments, the organic layer of the device further comprises ahost.

In some such embodiments, the host comprises a triphenylene containingbenzo-fused thiophene or benzo-fused furan, wherein any substituent inthe host is an unfused substituent independently selected from the groupconsisting of C_(n)H_(2n+1), OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂,N(Ar₁)(Ar₂), CH═CH—C_(n)H_(2n+1), C≡C—C_(n)H_(2n+1), Ar₁, Ar₁-Ar₂,C_(n)H_(2n)—Ar₁, or no substitution, wherein n is from 1 to 10, andwherein Ar₁ and Ar₂ are independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof. In some such embodiments, the host is acompound selected from the group consisting of:

and combinations thereof.

In some other embodiments, the host comprises a metal complex. In somefurther embodiments, the host comprises at least one of the chemicalgroups selected from the group consisting of carbazole, dibenzothiphene,dibenzofuran, dibenzoselenophene, azacarbazole, aza-dibenzothiophene,aza-dibenzofuran, and aza-dibenzoselenophene.

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, compoundsdisclosed herein may be used in conjunction with a wide variety ofhosts, transport layers, blocking layers, injection layers, electrodesand other layers that may be present. The materials described orreferred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but not limit to: aphthalocyanine or porphryin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butnot limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, azulene; group consisting aromaticheterocyclic compounds such as dibenzothiophene, dibenzofuran,dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene,benzoselenophene, carbazole, indolocarbazole, pyridylindole,pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole,oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine,pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine,indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole,benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline,quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine,phenazine, phenothiazine, phenoxazine, benzofuropyridine,furodipyridine, benzothienopyridine, thienodipyridine,benzoselenophenopyridine, and selenophenodipyridine; and groupconsisting 2 to 10 cyclic structural units which are groups of the sametype or different types selected from the aromatic hydrocarbon cyclicgroup and the aromatic heterocyclic group and are bonded to each otherdirectly or via at least one of oxygen atom, nitrogen atom, sulfur atom,silicon atom, phosphorus atom, boron atom, chain structural unit and thealiphatic cyclic group. Wherein each Ar is further substituted by asubstituent selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

k is an integer from 1 to 20; X¹ to X⁸ is C (including CH) or N; Ar¹ hasthe same group defined above.

Examples of metal complexes used in HIL or HTL include, but not limit tothe following general formula:

M is a metal, having an atomic weight greater than 40; (Y¹-Y²) is abidentate ligand, Y¹ and Y² are independently selected from C, N, O, P,and S; L is an ancillary ligand; m is an integer value from 1 to themaximum number of ligands that may be attached to the metal; and m+n isthe maximum number of ligands that may be attached to the metal.

In one aspect, (Y¹-Y²) is a 2-phenylpyridine derivative.

In another aspect, (Y¹-Y²) is a carbene ligand.

In another aspect, M is selected from Ir, Pt, Os, and Zn.

In a further aspect, the metal complex has a smallest oxidationpotential in solution vs. Fc⁺/Fc couple less than about 0.6 V.

In addition to the host materials described above, the device mayfurther comprise other host materials. Examples of such other hostmaterial are not particularly limited, and any metal complexes ororganic compounds may be used as long as the triplet energy of the hostis larger than that of the dopant. While the Table below categorizeshost materials as preferred for devices that emit various colors, anyhost material may be used with any dopant so long as the tripletcriteria are satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

M is a metal; (Y³-Y⁴) is a bidentate ligand, Y³ and Y⁴ are independentlyselected from C, N, O, P, and S; L is an ancillary ligand; m is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and m+n is the maximum number of ligands that maybe attached to the metal.

In one aspect, the metal complexes are:

(O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

In another aspect, M is selected from Ir and Pt.

In a further aspect, (Y³-Y⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; groupconsisting aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and group consisting 2 to 10 cyclic structural units which are groups ofthe same type or different types selected from the aromatic hydrocarboncyclic group and the aromatic heterocyclic group and are bonded to eachother directly or via at least one of oxygen atom, nitrogen atom, sulfuratom, silicon atom, phosphorus atom, boron atom, chain structural unitand the aliphatic cyclic group. Wherein each group is furthersubstituted by a substituent selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

In one aspect, host compound contains at least one of the followinggroups in the molecule:

R¹ to R⁷ is independently selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof, when it is aryl or heteroaryl, it has the similardefinition as Ar's mentioned above; k is an integer from 0 to 20; X¹ toX⁸ are selected from C (including CH) or N; and Z¹ and Z² are selectedfrom NR¹, O, or S.

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

k is an integer from 0 to 20; L is an ancillary ligand, m is an integerfrom 1 to 3.

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

R¹ is selected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is arylor heteroaryl, it has the similar definition as Ar's mentioned above;Ar¹ to Ar^(a) has the similar definition as Ar's mentioned above; k isan integer from 0 to 20; X¹ to X⁸ is selected from C (including CH) orN.

In another aspect, the metal complexes used in ETL contains, but notlimit to the following general formula:

(O—N) or (N—N) is a bidentate ligand, having metal coordinated to atomsO, N or N, N; L is an ancillary ligand; m is an integer value from 1 tothe maximum number of ligands that may be attached to the metal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table 1below. Table 1 lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

TABLE 1 MATERIAL EXAMPLES OF MATERIAL PUBLICATIONS Hole injectionmaterials Phthalocyanine and porphryin compounds

Appl. Phys. Lett. 69, 2160 (1996) Starburst triarylamines

J. Lumin. 72-74, 985 (1997) CF_(x) Fluoro- hydrocarbon polymer

Appl. Phys. Lett. 78, 673 (2001) Conducting polymers (e.g., PEDOT:PSS,polyaniline, polypthiophene)

Synth. Met. 87, 171 (1997) WO2007002683 Phosphonic acid and sliane SAMs

US20030162053 Triarylamine or polythiophene polymers with conductivitydopants

 

 

EP1725079A1 Organic compounds with conductive inorganic compounds, suchas molybdenum and tungsten oxides

US20050123751 SID Symposium Digest, 37, 923 (2006) WO2009018009 n-typesemiconducting organic complexes

US20020158242 Metal organometallic complexes

US20060240279 Cross-linkable compounds

US20080220265 Polythiophene based polymers and copolymers

WO 2011075644 EP2350216 Hole transporting materials Triarylamines (e.g.,TPD, α-NPD)

Appl. Phys. Lett. 51, 913 (1987)

US5061569

EP650955

J. Mater. Chem. 3, 319 (1993)

Appl. Phys. Lett. 90, 183503 (2007)

Appl. Phys. Lett. 90, 183503 (2007) Triaylamine on spirofluorene core

Synth. Met. 91, 209 (1997) Arylamine carbazole compounds

Adv. Mater. 6, 677 (1994), US20080124572 Triarylamine with(di)benzothiophene/ (di)benzo- furan

US20070278938, US20080106190 US20110163302 Indolocarbazoles

Synth. Met. 111, 421 (2000) Isoindole compounds

Chem. Mater. 15, 3148 (2003) Metal carbene complexes

US20080018221 Phosphorescent OLED host materials Red hostsArylcarbazoles

Appl. Phys. Lett. 78, 1622 (2001) Metal 8-hydroxy- quinolates (e.g.,Alq₃, BAlq)

Nature 395, 151 (1998)

US20060202194

WO2005014551

WO2006072002 Metal phenoxy- benzothiazole compounds

Appl. Phys. Lett. 90, 123509 (2007) Conjugated oligomers and polymers(e.g., polyfluorene)

Org. Electron. 1, 15 (2000) Aromatic fused rings

WO2009066779, WO2009066778, WO2009063833, US20090045731, US20090045730,WO2009008311, US20090008605, US20090009065 Zinc complexes

WO2010056066 Chrysene based compounds

WO2011086863 Green hosts Arylcarbazoles

Appl. Phys. Lett. 78, 1622 (2001)

US20030175553

WO2001039234 Aryltriphenylene compounds

US20060280965

US20060280965

WO2009021126 Poly-fused heteroaryl compounds

US20090309488 US20090302743 US20100012931 Donor acceptor type molecules

WO2008056746

WO2010107244 Aza-carbazole/ DBT/DBF

JP2008074939

US20100187984 Polymers (e.g., PVK)

Appl. Phys. Lett. 77, 2280 (2000) Spirofluorene compounds

WO2004093207 Metal phenoxy- benzooxazole compounds

WO2005089025

WO2006132173

JP200511610 Spirofluorene- carbazole compounds

JP2007254297

JP2007254297 Indolocabazoles

WO2007963796

WO2007063754 5-member ring electron deficient heterocycles (e.g.,triazole, oxadiazole)

J. Appl. Phys. 90, 5048 (2001)

WO2004107822 Tetraphenylene complexes

US20050112407 Metal phenoxypyridine compounds

WO2005030900 Metal coordination complexes (e.g., Zn, Al withN{circumflex over ( )}N ligands)

US20040137268, US20040137267 Blue hosts Arylcarbazoles

Appl. Phys. Lett, 82, 2422 (2003)

US20070190359 Dibenzothiophene/ Dibenzo- furan-carbazole compounds

WO2006114966, US20090167162

US20090167162

WO2009086028

US20090030202, US20090017330

US20100084966 Silicon aryl compounds

US20050238919

WO2009003898 Silicon/ Germanium aryl compounds

EP2034538A Aryl benzoyl ester

WO2006100298 Carbazole linked by non- conjugated groups

US20040115476 Aza-carbazoles

US20060121308 High triplet metal organometallic complex

US7154114 Phosphorescent dopants Red dopants Heavy metal porphyrins(e.g., PtOEP)

Nature 395, 151 (1998) Iridium(III) organometallic complexes

Appl. Phys. Lett. 78, 1622 (2001)

US2006835469

US2006835469

US20060202194

US20060202194

US20070087321

US20080261076 US20100090591

US20070087321

Adv. Mater. 19, 739 (2007)

WO2009100991

WO2008101842

US7232618 Platinum(II) organometallic complexes

WO2003040257

US20070103060 Osminum(III) complexes

Chem. Mater. 17, 3532 (2005) Ruthenium(II) complexes

Adv. Mater. 17, 1059 (2005) Rhenium (I), (II), and (III) complexes

US20050244673 Green dopants Iridium(III) organometallic complexes

Inorg. Chem. 40, 1704 (2001)

US20020034656

US7332232

US20090108737

WO2010028151

EP1841834B

US20060127696

US20090039776

US6921915

US20100244004

US6687266

Chem. Mater. 16, 2480 (2004)

US20070190359

US 20060008670 JP2007123392

WO2010086089, WO2011044988

Adv. Mater. 16, 2003 (2004)

Angew. Chem. Int. Ed. 2006, 45, 7800

WO2009050290

US20090165846

US20080015355

US20010015432

US20100295032 Monomer for polymeric metal organometallic compounds

US7250226, US7396598 Pt(II) organometallic complexes, includingpolydentated ligands

Appl. Phys. Lett. 86, 153505 (2005)

Appl. Phys. Lett. 86, 153505 (2005)

Chem. Lett. 34, 592 (2005)

WO2002015645

US20060263635

US20060182992 US20070103060 Cu complexes

WO2009000673

US20070111026 Gold complexes

Chem. Commun. 2906 (2005) Rhenium(III) complexes

Inorg. Chem. 42, 1248 (2003) Osmium(II) complexes

US7279704 Deuterated organometallic complexes

US20030138657 Organometallic complexes with two or more metal centers

US20030152802

US7090928 Blue dopants Iridium(III) organometallic complexes

WO2002002714

WO2006009024

US20060251923 US20110057559 US20110204333

US7393599, WO2006056418, US20050260441, WO2005019373

US7534505

WO2011051404

US7445855

US20070190359, US20080297033 US20100148663

US7338722

US20020134984

Angew. Chem. Int. Ed. 47, 1 (2008)

Chem. Mater. 18, 5119 (2006)

Inorg. Chem. 46, 4308 (2007)

WO2005123873

WO2005123873

WO2007004380

WO2006082742 Osmium(II) complexes

US7279704

Organo- metallics 23, 3745 (2004) Gold complexes

Appl. Phys. Lett. 74, 1361 (1999) Platinum(II) complexes

WO2006098120, WO2006103874 Pt tetradentate complexes with at least onemetal- carbene bond

US7655323 Exciton/hole blocking layer materials Bathocuprine compounds(e.g., BCP, BPhen)

Appl. Phys. Lett. 75, 4 (1999)

Appl. Phys. Lett. 79, 449 (2001) Metal 8- hydroxyquinolates (e.g., BAlq)

Appl. Phys. Lett. 81, 162 (2002) 5-member ring electron deficientheterocycles such as triazole, oxadiazole, imidazole, benzoimidazole

Appl. Phys. Lett. 81, 162 (2002) Triphenylene compounds

US20050025993 Fluorinated aromatic compounds

Appl. Phys. Lett. 79, 156 (2001) Phenothiazine- S-oxide

WO2008132085 Silylated five-membered nitrogen, oxygen, sulfur orphosphorus dibenzoheterocycles

WO2010079051 Aza-carbazoles

US20060121308 Electron transporting materials Anthracene- benzoimidazolecompounds

WO2003060956

US20090179554 Aza triphenylene derivatives

US20090115316 Anthracene- benzothiazole compounds

Appl. Phys. Lett. 89, 063504 (2006) Metal 8- hydroxyquinolates (e.g.,Alq₃, Zrq₄)

Appl. Phys. Lett. 51, 913 (1987) US7230107 Metal hydroxybeno- quinolates

Chem. Lett. 5, 905 (1993) Bathocuprine compounds such as BCP, BPhen, etc

Appl. Phys. Lett. 91, 263503 (2007)

Appl. Phys. Lett. 79, 449 (2001) 5-member ring electron deficientheterocycles (e.g., triazole, oxadiazole, imidazole, benzoimidazole)

Appl. Phys. Lett. 74, 865 (1999)

Appl. Phys. Lett. 55, 1489 (1989)

Jpn. J. Apply. Phys. 32, L917 (1993) Silole compounds

Org. Electron. 4, 113 (2003) Arylborane compounds

J. Am. Chem. Soc. 120, 9714 (1998) Fluorinated aromatic compounds

J. Am. Chem. Soc. 122, 1832 (2000) Fullerene (e.g., C60)

US20090101870 Triazine complexes

US20040036077 Zn (N{circumflex over ( )}N) complexes

US6528187

EXPERIMENTAL Compound Examples

Some of the substituted imidazole carbene complexes were synthesized asfollows.

Synthesis of Compound 1.

Iridium Heteroleptic Compound

Into a solution of 3-bromobenzo[b]thiophene (40 g, 190 mmol) in glacialacetic acid (140 ml) was added a solution of nitric acid (74 ml, 1760mmol) in glacial acetic acid (40 mL) over a period of 45 min. Thereaction mixture was stirred at room temperature for 5 hours beforequenching with water. The precipitate was isolated by filtration, washedwith water and recrystallized from ethyl acetate/hexane (1/1, v/v) toyield 3-bromo-2-nitrobenzo[b]thiophene (35 g, 72%) as yellow crystals.

A mixture solution of 3-bromo-2-nitrobenzo[b]thiophene (14 g, 54 mmol),aniline (14 ml, 154 mmol) and triethylamine (11 ml, 79 mmol) in DMF (150ml) was heated at 120° C. for 30 min before quenching with water. Thesolid was isolated by filtration, washed with water and recrystallizedfrom DCM/hexane to yield 2-nitro-N-phenylbenzo[b]thiophen-3-amine (14 g,96%) as a yellow solid.

Into a solution of 2-nitro-N-phenylbenzo[b]thiophen-3-amine (13 g, 48mmol) in acetic acid (200 ml) and water (20 ml) was added portionwiseiron powder (14 g, 250 mmol). After stirring at room temperature for 2h, it was filtered through a short plug of Celite and washed with DCM.The combined filtrate was washed with water and aqueous sodium carbonatesolution. Upon evaporation off the solvent, the residue was purified bycolumn chromatography on silica gel with hexane/DCM (4/1, v/v) as eluentto yield N³-phenylbenzo[b]thiophene-2,3-diamine (7.5 g, 65%) as a whitesolid.

Into a solution of N³-phenylbenzo[b]thiophene-2,3-diamine (16 g, 66.7mmol) in trimethoxymethane (200 ml) was added formic acid (1.5 ml, 42.3mmol) at room temperature. The reaction mixture was subsequently heatedat 120° C. for 6 h. After cooling to room temperature, it was quenchedwith aqueous NaHCO₃ solution and extracted with ethyl acetate. Uponevaporation off the solvent, the residue was purified by chromatographyon silica gel with hexane/EtOAc (95/5, v/v) as eluent to yield1-phenyl-1H-benzo[4,5]thieno[2,3-d]imidazole (9.0 g, 54%) as a solid.

A solution of 1-phenyl-1H-benzo[4,5]thieno[2,3-d]imidazole (4 g, 16mmol) and methyl iodide (11.36 g, 80 mmol) in EtOAc (100 ml) was stirredfor 48 h at room temperature. The precipitate was isolated by filtrationand washed thoroughly with EtOAc to yield3-methyl-1-phenyl-1H-benzo[4,5]thieno[2,3-d]imidazol-3-ium iodide (5.52g, 88%) as a white solid.

A mixture of 3-methyl-1-phenyl-1H-benzo[4,5]thieno[2,3-d]imidazol-3-iumiodide (2.5 g, 6.37 mmol) and Ag₂O (0.738 g, 3.19 mmol) in acetonitrile(150 ml) was stirred at room temperature under nitrogen overnight. Uponevaporation off the solvent, dimer (3.16 g, 1.89 mmol) and THF (150 ml)was introduced and the reaction mixture was refluxed under nitrogenovernight. After cooling to room temperature, it was filtered through ashort plug of Celite and the solid was washed with DCM. The combinedfiltrate was evaporated and purified by column chromatography onTEA-treated silica gel with hexane/DCM (9/1, v/v) as eluent as eluent toyield the mer form of the Ir heteroleptic compound (3.0 g, 75%) as ayellow solid.

The mer form of the product (2.0 g, 1.88 mmol) was dissolved in DMSO(150 ml) and irradiated with UV light (360 nm) under nitrogen for 2 h.Upon evaporation off the solvent under reduced pressure, the residue waspurified by column chromatography on TEA-treated silica gel with hexaneas eluent followed by extraction successively with hexane and methanolto yield the fac form of the product (1.4 g, 70%) as a yellow solid,identified as Compound 1.

COMPUTATIONAL EXAMPLES

Compound 1 and comparative compound (CC-1) were subjected to DFTcomputational investigation using the Gaussian software package at theB3LYP/cep-31 g functional and basis set. It was found that Compound 1has a triplet energy (T1) of 2.67 eV (464 nm), which will emit a bluecolor, whereas CC-1 has a T1 of 2.24 eV (552 nm), which will emit ayellow color. The enhanced T1 of Compound 1 is attributable to the5-membered heterocycle thieno ring fused to the imidazole ring. On theother hand, CC-1 has a phenyl ring fused to the imidazole ring, leadingto lower triplet energy. Since a high triplet energy is beneficial foremission in shorter wavelength region, it is concluded that metalcomplexes containing ligand of Formula I are advantageous over thosethat do not have the 5-membered heterocycle rings.

DEVICE EXAMPLES Example 1

An example device was fabricated by high vacuum (<10⁻⁷ Torr) thermalevaporation (VTE). The anode electrode is 800 Å of indium tin oxide(ITO). The cathode consisted of 10 Å of UF followed by 1,000 Å of Al.The device was encapsulated with a glass lid sealed with an epoxy resinin a nitrogen glove box (<1 ppm of H₂O and O₂) immediately afterfabrication, and a moisture getter was incorporated inside the package.

The organic stack of the OLED device used has the following structure:from the ITO surface, 100 Å of LG101 (LG Chem) as the hole injectionlayer, 300 Å of NPD doped with 2 weight percent of Alq as the holetransporting layer (HTL), 300 Å of Compound H doped with 15 weightpercent of Compound 1 as the emissive layer (EML), 50 Å of Compound H asthe Blocking Layer (BL) and 400 Å of Alq as the electron transport layer(ETL).

Under a driving voltage of 7.4 V, the device achieves a current densityof 10 mA/cm² and a sky-blue emission with 1931 CIE coordinate of (0.195,0.322) and a current efficiency of 0.8 cd/A.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

We claim:
 1. A compound comprising a ligand L₃ of Formula (I):

wherein ring B is a 5-member aromatic heterocyclic ring containing atleast one heteroatom selected from the group consisting of N, O, and S;wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclicring; wherein R_(A) represents mono, di, tri, tetra substitutions or nosubstitution; wherein R₁ represents mono, di, or tri substitution or nosubstitution; wherein each R_(A), R₁ and R₂ is independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein any twoadjacent substituents are optionally joined to form a ring, which can befurther substituted; wherein Z₁ is nitrogen or carbon; wherein theligand L₃ is coordinated to a metal M₁; and wherein the ligand L₃ isoptionally linked with other ligands to comprise a tridentate,tetradentate, pentadentate or hexadentate ligand.
 2. The compound ofclaim 1, wherein M₁ is selected from the group consisting of Ir, Rh, Re,Ru, Os, Pt, Au, and Cu.
 3. The compound of claim 1, wherein M₁ is Ir orPt.
 4. The compound of claim 1, wherein ligand L₃ is selected from thegroup consisting of:

wherein A₁, A₂, and A₃ are independently selected from the groupconsisting of carbon, nitrogen, oxygen, and sulfur, and at least one ofA₁, A₂, and A₃ is not carbon.
 5. The compound of claim 4, wherein theligand L₃ is selected from the group consisting of:

wherein A₁ and A₃ are independently selected from the group consistingof oxygen, nitrogen, and sulfur; wherein R₃ represents mono, di, tri, ortetra substitution, or no substitution; and wherein R₃ is independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein anytwo adjacent substituents are optionally joined to form into a ring,which can be further substituted.
 6. The compound of claim 5, whereinthe ligand L₃ is selected from the group consisting of:


7. The compound of claim 1, where the compound is a compound of Formula(II):

wherein -L₁-L₂- is a bidentate ligand selected from the group consistingof:

wherein R_(a), R_(b), and R_(c) represent mono, di, tri or tetrasubstitutions; wherein R_(a), R_(b), and R_(c) are each independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein anytwo adjacent substituents of R_(a), R_(b), and R_(c) are optionallyjoined to form a ring, which can be further substituted; and wherein nis 1, 2 or
 3. 8. The compound of claim 1, wherein the compound is acompound of Formula (III):

wherein -L₁-L₂- is a bidentate ligand; and wherein m is 1 or
 2. 9. Thecompound of claim 8, wherein the compound is a compound of Formula (IV):

wherein -L₁-L₂- is a bidentate ligand; and wherein X is selected from agroup consisting of O, S, NR, CR′R″, SiR′R″; wherein R, R′, and R″ areindependently selected from the group consisting of alkyl, aryl andheteroaryl, wherein R′ and R″ are optionally linked; and wherein any twoadjacent substituents are optionally joined to form into a ring, whichcan be further substituted.
 10. The compound of claim 9, wherein thecompound is a compound of Formula (V):


11. The compound of claim 1, wherein the compound is a compound ofFormula (VI):

wherein X and Y are independently selected from a group consisting of O,S, NR, CR′R″, and SiR′R″; and wherein R, R′, and R″ are independentlyselected from the group consisting of alkyl, aryl, and heteroaryl; andwherein any two adjacent substituents are optionally joined to form intoa ring, which can be further substituted.
 12. The compound of claim 11,wherein the compound is a compound of Formula (VII):


13. The compound of claim 1, wherein the compound is selected from thegroup consisting of:


14. The compound of claim 1, wherein the compound is selected from thegroup consisting of:


15. A first device comprising a first organic light emitting device,further comprising: an anode; a cathode; and an organic layer, disposedbetween the anode and the cathode, comprising a compound comprising aligand L₃ of Formula (I):

wherein ring B is a 5-member aromatic heterocyclic ring containing atleast one heteroatom selected from the group consisting of N, O, and S;wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclicring; wherein R_(A) represents mono, di, tri, tetra substitutions or nosubstitution; wherein R₁ represents mono, di, or tri substitution or nosubstitution; wherein each R_(A), R₁ and R₂ is independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein any twoadjacent substituents are optionally joined to form a ring, which can befurther substituted; wherein Z₁ is nitrogen or carbon; wherein theligand L₃ is coordinated to a metal M₁; and wherein the ligand L₃ isoptionally linked with other ligands to comprise a tridentate,tetradentate, pentadentate or hexadentate ligand.
 16. The first deviceof claim 15, wherein the first device is a consumer product.
 17. Thefirst device of claim 15, wherein the first device is an organiclight-emitting device.
 18. The first device of claim 15, wherein thefirst device comprises a lighting panel.
 19. The first device of claim15, wherein the organic layer is an emissive layer and the compound isan emissive dopant.
 20. The first device of claim 15, wherein theorganic layer is an emissive layer and the compound is a non-emissivedopant.
 21. The first device of claim 15, wherein the organic layerfurther comprises a host.
 22. The first device of claim 21, wherein thehost comprises a triphenylene containing benzo-fused thiophene orbenzo-fused furan; wherein any substituent in the host is an unfusedsubstituent independently selected from the group consisting ofC_(n)H_(2n+1), OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂),CH═CH—C_(n)H_(2n+1), C≡C—C_(n)H_(2n+1), Ar₁, Ar₁-Ar₂, C_(n)H_(2n)—Ar₁,or no substitution; wherein n is from 1 to 10; and wherein Ar₁ and Ar₂are independently selected from the group consisting of benzene,biphenyl, naphthalene, triphenylene, carbazole, and heteroaromaticanalogs thereof.
 23. The first device of claim 21, wherein the host isselected from the group consisting of:

and combinations thereof.
 24. The first device of claim 21, wherein thehost comprises a metal complex.
 25. The first device of claim 21,wherein the host comprises at least one of the chemical groups selectedfrom the group consisting of carbazole, dibenzothiphene, dibenzofuran,dibenzoselenophene, azacarbazole, aza-dibenzothiophene,aza-dibenzofuran, and aza-dibenzoselenophene.